This invention relates to creation of electrical coronas, and in particular to an electrode for creation of a corona for surface treating desired areas of plastics and other materials.
As explained in my U.S. Pat. No. 4,693,869, the disclosure of which is incorporated herein by reference, many plastics, when molded, will not accept an adhesive, a coating, or inks or other printing vehicles unless the surface of the plastic has been chemically and/or physical altered. My patent discloses an electrode arrangement for creating a corona for treating such surfaces to accept adhesives, coatings, inks or other materials applied to the surface. One form of that patent pertains to a disk-like electrode which is able to create a corona in an annular fashion only because a corona will not be emitted from any portion other than the outer periphery of the electrode, thus leaving a circular central area without any treating corona.
My U.S. Pat. No. 4,924,092, the disclosure of which is also incorporated herein by reference, is directed to a unique system for creating a uniform corona over a predetermined volume of free space, so that surfaces of a plastic or similar material can be treated on all sides at one time, rather than on only a single side. In both referenced patents, a high frequency electric corona generator is used to generate resonate frequencies on the order to 2 MHz and above.
In my U.S. patent application Ser. No. 461,334, filed Jan. 5, 1990, the disclosure of which is also incorporated herein by reference, I disclose a particular form of electrode arrangement for creating corona over an area, using a disk-like electrode which has a series of spaced concentric rings, each of which creates a corona, thus providing an electrode which provides a corona over an area, rather than only an annular ring.